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Author Topic: Babble’s Believe it or Not
Zatamon
rabble-rouser
Babbler # 1394

posted 07 August 2002 03:48 PM      Profile for Zatamon     Send New Private Message      Edit/Delete Post  Reply With Quote 
Experimental evidence proving that we have to choose to give up either objectivity or causality (or both).

A series of experiments were carried out in Paris in the 1980-s by Alain Aspect and his associates to prove or disprove predictions of the EPR (Einstein-Podolsky-Rosen) thought-experiment.

Rather than measuring the momentum of electrons, Aspect measured the polarization of photons, which can be done much more accurately. Polarization is subject to a different conservation law the conservation of angular momentum, which governs the spin and rotational or angular motion of material bodies.

The basic idea was the same to observe the polarization of two correlated photons (rather than the momentum of two correlated electrons), and to see whether measuring one photon had any statistical effect on the other. Aspect's results as interpreted by Bell's theorem vindicated the probabilistic predictions of quantum theory, beyond any reasonable doubt.

The experiments seemed to show that one photon somehow "knows" what the other is doing. Measuring the polarization of one of the photons has an apparent effect on the other, even though there is no mechanism by which they can "communicate." Uncertainty or probability seems to pass magically from one photon to the other and to affect its statistical behavior.

In one of the experiments, there was not enough time for a signal even at the speed of light to travel from one photon to the other. It seemed impossible for the photons to "communicate" with and influence each other. Yet they did. Einstein's "spooky actions at a distance" seem to be real and to occur instantaneously.

EPR had always assumed that if a physical quantity (momentum or polarization, for example) can be measured without disturbing the system, then that quantity must have an independent objective reality. But neither the inferred momentum of an electron nor the inferred polarization of a photon can exhibit such an independent objective existence.

EPR had assumed objectivity and causality and concluded that quantum theory was incomplete. Bell and Aspect, however, had demonstrated the completeness of quantum theory.

One must therefore choose to give up either objectivity or causality (or both).

I thought that this thread could be a collection of weird and wonderful, well-documented mysteries in science or in any other walks of life.

Something like “Babble’s Believe it or Not”

[ August 07, 2002: Message edited by: Zatamon ]


From: where hope for 'hope' is contemplated | Registered: Sep 2001  |  IP: Logged
DrConway
rabble-rouser
Babbler # 490

posted 07 August 2002 08:32 PM      Profile for DrConway     Send New Private Message      Edit/Delete Post  Reply With Quote 
Quantum mechanics already violates notions of causality in part because of a model that can treat virtual particles as travelling back and forth through time rather than the more conventional method of treating their presence and extinguishment as a product of small violations of conservation of energy.
From: You shall not side with the great against the powerless. | Registered: May 2001  |  IP: Logged

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